In situ production of a two-dimensional molybdenum disulfide/graphene hybrid nanosheet anode for lithium-ion batteries

Nanoarchitected graphene/copper oxide nanoparticles/MoS2 ternary thin films as highly efficient electrodes for aqueous sodium-ion batteries

Sodium-ion batteries (SIBs) operating in aqueous electrolyte are an emerging technology that promises to be safer, cheaper, more sustainable and more efficient than their lithium-based counterparts. One of the great challenges associated with this technology is the development of advanced materials with high specific capacity to be used as electrodes. Herein, we describe an ingenious strategy to prepare unprecedented tri-component nanoarchitected thin films with superior performance when applied as anodes in aqueous SIBs. Taking advantage of the broadness and versatility of the liquid-liquid interfacial route, three transparent nanocomposite films comprising graphene, molybdenum sulphide and copper oxide nanoparticles have been prepared. The samples were characterized using several techniques, and the results demonstrated that depending on the specific experimental strategy, different nanoarchitectures are achieved, resulting in different and improved properties. An astonishing capacity of 1377 mA h g-1 at 0.1 A g-1 and a degree of recovery of 100% were observed for the film in which the interactions among the components were optimized. This is among the highest capacity values reported in the literature and demonstrates the potential of these tri-component materials to be used as anodes in aqueous sodium-ion batteries.

Engineering active heterojunction architecture with oxygenated-Co, Mo bimetallic sulfide heteronanosheet and graphene oxide for peroxymonosulfate activation

Bimetallic sulfides have distinctive catalytic property in activating peroxymonosulfate (PMS) for water remediation. Polyoxometalates as potential precursors have rarely been reported for the catalytic degradation of refractory organic pollutants. Herein, a composite catalyst of Co-Mo bimetallic sulfides supported onto graphene oxide (O-CoMoS/GO) with a heterojunction architecture was synthesized through a hydrothermal strategy with polyoxometalates ((NH₄)₄[Co^IIMo₆O₂₄H₆]·6H₂O) as the precursor and applied in the PMS activation. This material showed a superior performance for the catalytic degradation of the model organic pollutant, 4-chlorophenol (rapidly removed within 10 min with an apparent reaction rate constant of 0.5458 min^-1). O-CoMoS/GO outperformed most of the reported catalysts in terms of activity and had a strong tolerance towards common organic and inorganic compounds in water, and could perform well in different real water systems. Experimental and theoretical results indicated that the introduction of GO could achieve the enrichment of electrons on the metals and reduce the d band center (ε_d) of Co close to the Fermi level (ε_F), thereby facilitating the interfacial electron transfer process. The activation mechanism was due to the as-prepared bimetallic sulfides and the formation of heterojunction structure with GO, where Co(II) as the active center could be regenerated by the adjacent Mo element (as co-catalyst) and by gathering electrons from GO through the Co/Mo-O-C coupling. This work provides insights into the design of bimetallic sulfide catalysts in activating PMS for water remediation.

Monodisperse MoS2/Graphite Composite Anode Materials for Advanced Lithium Ion Batteries

Traditional graphite anode material typically shows a low theoretical capacity and easy lithium decomposition. Molybdenum disulfide is one of the promising anode materials for advanced lithium-ion batteries, which possess low cost, unique two-dimensional layered structure, and high theoretical capacity. However, the low reversible capacity and the cycling-capacity retention rate induced by its poor conductivity and volume expansion during cycling blocks further application. In this paper, a collaborative control strategy of monodisperse MoS₂/graphite composites was utilized and studied in detail. MoS₂/graphite nanocomposites with different ratios (MoS₂:graphite = 20%:80%, 40%:60%, 60%:40%, and 80%:20%) were prepared by mechanical ball-milling and low-temperature annealing. The graphite sheets were uniformly dispersed between the MoS₂ sheets by the ball-milling process, which effectively reduced the agglomeration of MoS₂ and simultaneously improved the electrical conductivity of the composite. It was found that the capacity of MoS₂/graphite composites kept increasing along with the increasing percentage of MoS₂ and possessed the highest initial discharge capacity (832.70 mAh/g) when MoS₂:graphite = 80%:20%. This facile strategy is easy to implement, is low-cost, and is cosmically produced, which is suitable for the development and manufacture of advance lithium-ion batteries.

TEMPO-oxidized nanofibrillated cellulose assisted exfoliation of MoS2/graphene composites for flexible paper-anodes

TEMPO-oxidized nanofibrillated cellulose (ONFC) with charged carboxyl groups is introduced for the efficient exfoliation of two-dimensional (2D) MoS2/graphene composites. As an effective dispersant agent, ONFC can be easily absorbed between the adjacent layers, so as to prevent the accumulation of the exfoliated nanosheets. With the assistance of charged ONFC, the exfoliated MoS2/graphene is gradually increased in the aqueous dispersions with the elongated sonication time. After dewatering, self-standing MoS2/Graphene/ONFC/CNTs composite films are rationally constructed using ONFC as flexible fibrous skeleton, and CNTs/graphene as 1D/2D interpenetrating electrical networks. Ultrathin MoS2 nanosheets anchored on the 1D/2D heterogeneous networks is directly acted as an ideal paper-anode for lithium-ion batteries (LIBs) without using traditional metallic current collector. The self-standing flexible electrode materials based on natural cellulose will promote the future green electronics with high flexibility, miniaturization, and increased portability.

Toward layered MoS2 anode for harvesting superior lithium storage

As a typical transition metal dichalcogenide (TMD), molybdenum disulphide (MoS₂) has become one of the most promising anode materials for lithium-ion batteries (LIBs) due to its desirable electrochemical properties. But the development of commercial MoS₂ is limited by the problem of agglomeration. Thus, the production of MoS₂ nanosheets with few (<10) layers is highly desired but remains a great challenge. In this work, a facile and scalable approach is developed to prepare large-flake, few-layer (4–8) MoS₂ nanosheets with the assistance of ultrasonics. Simultaneously, the as-prepared MoS₂ nanosheets and commercial bulk MoS₂ were analysed under multiple spectroscopic techniques and a series of electrochemical tests to understand the dependence of electrochemical performance on structural properties. When used as anode materials for LIBs, the obtained MoS₂ nanosheets provide a reversible capacity of 716 mA h g⁻¹ at 100 mA g⁻¹ after 285 cycles, and demonstrated an excellent capacity retention rate of up to 80%. Compared with that of commercial MoS₂ (14.8%), the capacity retention rate of our MoS₂ nanosheets has a significant improvement. This work explored the ability of few-layered MoS₂ nanosheets in the field of LIBs while suggesting the commercialization of the MoS₂ by an ultrasonicated ball milling exfoliation technique.

A facile and scalable approach is developed to prepare large-flake, few-layer (4–8) MoS₂ nanosheets with the assistance of ultrasonics.

Mechanochemistry: A force in disguise and conditional effects towards chemical reactions

Mechanochemistry refers to unusual chemical reactions induced by mechanical energy at room temperatures. It has attracted increased attention because of advantages, such as being a solution-free, energy saving, high-productivity and low-temperature process. However, there is limited understanding of the mechanochemical process because mechanochemistry is often conducted using closed milling devices, which are often regarded as a black box. This feature article shows that mechanochemical reactions can be controlled by varying milling parameters, such as the mechanical force, milling intensity, time and atmosphere. New nanomaterials with doped and functionalized structures can be produced under controlled conditions, which provide a critical insight for understanding mechanochemistry. A fundamental mechanism investigation using force microscopy is discussed.

Recent advances on TMDCs for medical diagnosis

Transition metal dichalcogenides (TMDCs), such as MoS₂ and WS₂, have attracted much attention in biosensing and bioimaging due to its excellent stability, biocompatibility, high specific surface area, and wide varieties. In this review, we overviewed the application of TMDCs in biosensing and bioimaging. Firstly, the synthesis methods and surface functionalization methods of TMDCs were summarized. Secondly, according to the working mechanism, we classified and gave a detailed account of the latest research progress of TMDC-based biosensing for the detection of the enzyme, DNA, and other biological molecules. Then, we outlined the recent progress of applying TMDCs in bio-imaging, including fluorescence, X-ray computed tomographic, magnetic response imaging, photographic and multimodal imaging, respectively. Finally, we discussed the future challenges and development direction of the application of TMDCs in medical diagnosis. Also, we put forward our view on the opportunity of TMDCs in the big data of modern medical diagnosis.